This invention relates to the achievement of low cost and versatile electroluminescent lamp products.
As is known by those in the art, an electroluminescent lamp is a surface-area light source consisting of a suitable phosphor placed between electrodes, one of which is essentially transparent. When an alternating current is applied between the electrodes the phosphor emits light, the color of the light is dependent on the choice of phosphor.
Such lamps are suitable for a wide variety of applications, including illuminated instrument panels, dial indicators, signs and the like. Such electroluminescent lamp panels can be fabricated by applying a general coating of conductive material, such as indium tin oxide, over the entire substrate panel, the coating providing the material for one of the electrodes, upon which the phosphor and rear electrode layers are applied. In many applications, the full surface of the panel is not required to be light-emitting and the unlit portion is masked by printing an opaque ink on the front surface of the lamp. Alternatively, as described in U.S. Pat. No. 4,904,901, material (indium tin oxide) corresponding to the transparent layer is deposited over an entire surface of the panel and is thereafter removed from most of the surface with an acid etch leaving behind areas corresponding to discrete areas of illumination. The phosphor and rear electrode layers are then deposited over the discrete areas. Likewise, either the phosphor or the rear electrode can be applied over desired areas using techniques well-known in the art.